Finita la conversione dei listati in file separati. Passato anche alla nuova

[gapil.git] / listati / Mutex.c

diff --git a/listati/Mutex.c b/listati/Mutex.c
new file mode 100644 (file)
index 0000000..3d0c4c0
--- /dev/null
+++ b/listati/Mutex.c
@@ -0,0 +1,49 @@
+/* Function MutexCreate: create a mutex/semaphore */
+int MutexCreate(key_t ipc_key) 
+{
+    const union semun semunion={1};             /* semaphore union structure */
+    int sem_id, ret;
+    sem_id = semget(ipc_key, 1, IPC_CREAT|0666);         /* get semaphore ID */
+    if (sem_id == -1) {                              /* if error return code */
+        return sem_id;
+    }
+    ret = semctl(sem_id, 0, SETVAL, semunion);             /* init semaphore */
+    if (ret == -1) {
+        return ret;
+    }
+    return sem_id;
+}
+/* Function MutexFind: get the semaphore/mutex Id given the IPC key value */
+int MutexFind(key_t ipc_key) 
+{
+    return semget(ipc_key,1,0);
+}
+/* Function MutexRead: read the current value of the mutex/semaphore */
+int MutexRead(int sem_id) 
+{
+    return semctl(sem_id, 0, GETVAL);
+}
+/* Define sembuf structures to lock and unlock the semaphore  */
+struct sembuf sem_lock={                                /* to lock semaphore */
+    0,                                   /* semaphore number (only one so 0) */
+    -1,                                    /* operation (-1 to use resource) */
+    SEM_UNDO};                                /* flag (set for undo at exit) */
+struct sembuf sem_ulock={                             /* to unlock semaphore */
+    0,                                   /* semaphore number (only one so 0) */
+    1,                                  /* operation (1 to release resource) */
+    SEM_UNDO};                                      /* flag (in this case 0) */
+/* Function MutexLock: to lock a mutex/semaphore */
+int MutexLock(int sem_id) 
+{
+    return semop(sem_id, &sem_lock, 1);
+}
+/* Function MutexUnlock: to unlock a mutex/semaphore */
+int MutexUnlock(int sem_id) 
+{
+    return semop(sem_id, &sem_ulock, 1);
+}
+/* Function MutexRemove: remove a mutex/semaphore */
+int MutexRemove(int sem_id) 
+{
+    return semctl(sem_id, 0, IPC_RMID);
+}